Embodiments are directed towards circuits utilized to energize power devices. More particularly, embodiments relate to a method and apparatus for a driver circuit utilized to energize a power device, where the driver circuit exhibits substantially no energy loss, and thus higher efficiency.
Traditionally, a MOSFET or IGBT is utilized as a power switch or power device, where gate control, i.e., turning ON and OFF of the power device, is achieved by charging and discharging an input capacitance of the power device. When the capacitance has a relatively simple charge and discharge circuit, energy received by the capacitance is dissipated in the active and passive components of a circuit. This loss of energy is acceptable when the value of the capacitance is low, e.g., 2 nF-5 nF, and the commutation frequency is also relatively low. A problem arises when the capacitance is increased to the 50 nF-100 nF range, and the commutation frequency is 100 kHz or more. In those cases, both the power dissipation and equipment size increase. This results in throwing away energy, which although may seem miniscule for each instance of time, dramatically increases in magnitude over time for limited energy systems, e.g., solar systems, and for loads that remain in an idle state continuously, i.e., requiring small amounts of energy for long periods of time.
One way to solve these problems has been to utilize resonant power exchange. However, this has several disadvantages, one of which is that the circuit must be relatively complex for high efficiency. Another way of solving these problems is to utilize drive switches to turn ON and OFF the main switches, which would connect the gate of the power device to a DC supply. This results in excess energy loss through heating of the device. For example, if you charge the power device capacitance to 10 V you throw away as much energy as you put into the capacitance. Then, when you turn off the power device to discharge it you throw that energy away. Thus, you lose half the energy turning it ON and half the energy turning it OFF. This has become even more of a problem as the power conversion frequency has increased into the megahertz range.
A still further way of solving these above problems has been to utilize a resonance gate driver circuit, where energy is pre-stored in an inductor. To turn ON the power device a user connects the gate of the power device to the inductor, which charges up the gate capacitance. To turn OFF the power device a user puts the energy stored in the gate capacitance back into the inductor and disconnects the gate. Although efficient, this system requires somewhat complex timing methods. This is due to the fact a user must know in advance that he is going to switch the power device ON because he needs to charge up the inductor before connecting it to the gate in order to power the device and turn it ON. This method also requires somewhat complex circuitry because there needs to be a charge and discharge circuit for the inductor. Also, there needs to be a control circuit connecting and disconnecting the inductor to the power device gate, so that after the power device gate capacitance is charged it is not discharged by the inductor. Thus, a user has to switch the inductor between a source and the power device, and then back again.
Therefore, a need exists for a highly efficient and simple circuit topology driving circuit to charge and discharge a gate capacitance to power a power device, while also maintaining linear charge and discharge waveforms. Also, a needs exists for the circuit to have short switching times to allow for short charge and discharge times, e.g., in the 40 nS to 60 nS range.
According a manifestation, a system is taught that may comprise a circuit board and a circuit. The circuit may comprise, in parallel, a power section, a rectifying section, a switching section, a capacitance, and an anti-spiking section. The circuit may further comprise a transformer section coupled to the rectifying section, the switching section, and the anti-spiking section and a power device coupled to a portion of the anti-spiking section. The system may be configured to regenerate substantially all energy utilized to power the power device via the coupling of the transformer section to the rectifying section, the switching section, the capacitance, and the anti-spike section.
In another manifestation a method may be taught for driving a gate of a power device coupled within a circuit operatively configured to substantially eliminate energy loss. The method may comprise powering the circuit with a power source. A first switch may be turned ON and a second switch may be turned OFF to allow energy from the power source to flow through the first switch to charge a power device capacitance, via an inductance, that turns ON a the power device, to charge a source capacitance, and to return a portion of the energy back to the power source. Energy from the inductance may be discharged to further charge the power device capacitance with the discharged energy from the inductance. The first switch may be turned OFF and the second switch may be turned ON to turn OFF the power device and to discharge the power device capacitance and to allow energy to flow from the power device capacitance to the source capacitance, via the inductance, to charge the source capacitance and return a portion of the energy to the power source. Finally, energy in the inductance may be discharged to further charge the source capacitance and return a portion of the energy to the power source.
A main advantage is that a simple design with no control circuit requirements can be used to power a gate of a power device by regenerating substantially all the energy used to charge up a gate capacitance through use of a transformer.